The need for an accurate, reliable method for testing for malabsorption which is simple enough to be utilized in the clinical situation and sufficiently economical for mass screening has been long felt. The malabsorption syndromes are clinical entities associated with defective absorption of amino acids, sugar, fat, vitamins and minerals. Malabsorption is thus the common denominator in a wide variety of clinical disorders the severity of which covers a broad range and which, when diagnosed, require individual analysis of each patient against the background of the normal process of absorption.
Among the conditions causing malabsorption can be named, for example: celiac sprue (idiopatic sprue in adults and celiac disease in children); Crohn's disease (ileitis, regional enteritis and jejuno ileitis); postsurgical malabsorption (e.g. from total gastrectomy, partial gastrectomy or selective or total vagotomy); short bowel syndrome; bacterial overgrowth of the small bowel (contaminated bowel syndrome); protein-losing gastroenteropathies (a number of abnormal conditions resulting in excessive loss of plasma protein into the gastrointestinal tract with resultant hypoproteinemia); radiation damage to the body (whole body radiation or radiation of the pelvic region); mesenteric artery insufficiency (which may be chronic or related to atherosclerosis); drug-induced malabsorption, particularly the antibiotics, e.g. neomycin, also anticonvulsants, colchicine and diuretics; malabsorption in the aged (mostly amino acids and sugars); tropical sprue, and subclinical malabsorption (tropical enteropathy). Malabsorption is not always accompanied by gross passage of abnormal stools, i.e. steatorrhea, as is incorrectly believed by many lay persons. In fact, unfortunately, most patients with malabsorption do not have steatorrhea and the correct diagnosis is often missed. Further, malabsorption of amino acids usually correlates with malabsorption of carbohydrates and/or fats.
There are a number of methods utilized presently to test for malabsorption. One such series of tests is intake-output balance tests involving fat, radioactive tracers or nitrogens. These tests are difficult to conduct and interpret, e.g. since intestinal motility and nutrient metabolism due to bacteria in the gastrointestinal tract detract from accuracy. The most commonly used screening method for malabsorption in the laboratory is the D-xylose absorption test.
The use of D-xylose as an absorption screening test has several disadvantages. First, the absorption of D-xylose, which occurs predominantly in the duodenum and jejunum, is dependent on a structurally intact small bowel. The absorption of D-xylose is decreased by any condition that alters the absorptive area or capacity of the small intestine. Second, D-xylose is about 60% metabolized. Experiments conducted with D-xylose tagged with .sup.14 C show substantial quantities of .sup.14 C incorporated into liver glycogen and also as CO.sub.2 in exhaled air.
Further, a considerable and variable amount of D-xylose may not be absorbed from the G.I. tract. The unabsorbed material may produce borborygmi, abdominal cramps and a temporary increase in diarrhea which itself may hinder absorption. Fourth, bacterial overgrowth proximal to the absorptive site may consume enough sugar to produce false low values. Finally, D-xylose is not well standardized due to considerable variance in accepted testing measures. This is, in part, due to the fact that the urine analysis for D-xylose is not specific.
In accordance with the present invention, a screening method for malabsorption is provided which suffers none of the foregoing disadvantageous properties and which facilitates quantitative determinations in the urine.